The present invention relates to a tool for cutting the wall of a pipe from inside the pipe.
In various industrial applications, it is necessary to cut the wall of a pipe at a location along the pipe which is not accessible readily from outside of the pipe. For example, when gas utility service to a building is to be terminated permanently, the service pipe leading from the gas main to the building usually is severed adjacent the main. Ordinarily, the portion of the service pipe which must be cut is buried beneath the ground. Therefore, if the pipe is to be cut from the outside, it must first be exposed by excavation. Such excavation is inconvenient and expensive. By contrast, if the pipe can be cut from the inside by a cutter disposed within the bore of the pipe, there will be no need to expose the outside of the pipe and hence no need for excavation.
Various devices have been proposed for cutting a pipe from the inside. As described in U.S. Pat. No. 3,293,963, issued Dec. 27, 1966 to J. J. Carroll et al., one such device includes a circular saw blade. A motor is provided to power the circular saw blade in rotation about its own axis; the motor and saw blade are placed into the pipe and retained against movement axially of the pipe by a hydraulically actuated gripper assembly which engages the pipe wall. Another hydraulically actuated device moves the circular saw radially of the pipe so that the circular saw cuts through the wall of the pipe at one spot. A hydraulic rotary actuator then swings the blade about the axis of the pipe after the blade has penetrated the pipe wall to extend the cut around the pipe.
Another internal pipe cutter is described in U.S. Pat. No. 4,177,558, issued Dec. 11, 1979 to T. G. Brown. This cutter includes a housing, a shaft rotatably mounted to the housing and a circular saw blade coaxially mounted to the shaft. In operation, the housing is positioned outside of the pipe adjacent an open end thereof so that the shaft protrudes into the pipe and the blade is positioned within the pipe. The shaft and blade are rotated, as by a motor, and the housing is manipulated to force the blade into engagement with the wall of the pipe and move the blade about the periphery of the pipe.
Another form of pipe cutter, described in U.S. Pat. No. 3,283,405, issued Nov. 8, 1966 to S. P. Braswell, incorporates a drive shaft, a plurality of cutting blades connected to the drive shaft for rotation therewith and means for forcing the blades radially outwardly within the pipe to engage them with the wall of the pipe in response to axial displacement of the drive shaft. A pipe wall gripping device is provided, such device being actuated by axial displacement of the drive shaft.
The pipe cutting device disclosed in U.S. Pat. No. 1,068,991, issued July 29, 1913 to W. E. Dunkerley et al, incorporates a body and a blade mounted to the body for pivoting motion about an axis parallel to the axis of the body. The body is inserted into the pipe to be cut and the body is rotated on its axis. Centrifugal force causes the blade to swing outwardly from the body and engage the wall of the pipe.
Other internal pipe and tube cutters are described in the following U.S. Pat. Nos. 1,007,330; 1,499,429; 2,538,890; and 3,939,561.